There are two types of heat calibration of titanium rod parts: hot forming and calibration in two processes, forming at one time; preforming and then heat calibration. The latter is to place the preform on a heated mold, preheat it to a specified temperature, maintain it for a certain period of time under pressure, perform a second forming or hot press calibration, and then take out the part.
Thermal correction is usually used to reduce dimensional errors or distortions of preforms made by other forming processes and improve part quality. Thermal correction can greatly reduce the angle and surface size deviations of titanium rod parts, shape deviations, bending radius deviations, ripples on the convex edges, wrinkles (except dead wrinkles) and distortions formed , as well as the warping or agitation of the web, etc., to obtain parts that meet the final profile requirements and have qualified quality.
The basic process of thermal calibration:
1. Install the mold on the hot press and preheat the mold in the heating furnace;
2. Heat the mold to the calibration temperature and stabilize the temperature;
3. Install the wool or preformed parts on the mold and heat it to the calibration temperature;
4. After closing the mold, apply sufficient pressure and maintain it for a certain period of time to obtain parts that meet the requirements;
5. Remove the part from the mold and allow it to cool evenly to room temperature.
It is crucial to ensure that the removed parts cool evenly. If a well-calibrated part has residual stress caused by a large temperature difference during cooling, the part will warp. To do this, the parts can be hung on special cooling racks or moved to asbestos mats to cool. If necessary, for some parts, a uniform heating plate or calibration fixture can be used to cool them at a slow speed or in a clamped state. Because cadmium (Cd), tin (Sn), lead (Pb) and zinc (Zn)-based alloys adhere to titanium rods at high temperatures, they will cause titanium to become brittle (such as "cadmium embrittlement"), and the parts will be damaged. Cracks or even complete damage may occur when exposed to force. Therefore, it is prohibited to use lead or lead-based alloys in molds or fixtures that come into contact with titanium. The use of zinc or tin-based alloy molds or fixtures and zinc-plated, tin or cadmium molds, fixtures or temporary fasteners is also prohibited when metal contamination is not removed as specified.
During hot calibration, the workpiece, mold, operating tools, etc. must be kept clean and must not contain dirt or any debris.
